Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$153.33	8.142%	$165.8141	$165.81	$165.80	$165.80
Purchase #2	$191.86	10.334%	$211.6868	$211.69	$211.70	$211.70
Purchase #3	$208.74	10.137%	$229.9	$229.90	$229.90	$229.90
Purchase #4	$24.43	4.695%	$25.577	$25.58	$25.60	$25.60
Purchase #5	$82.52	3.517%	$85.4222	$85.42	$85.40	$85.40
Purchase #6	$90.39	4.267%	$94.2469	$94.25	$94.25	$94.20
Purchase #7	$230.70	7.129%	$247.1466	$247.15	$247.15	$247.10
7 purchase totals =	$981.97		$1,059.7936	$1,059.80	$1,059.80	$1,059.70